Improved hydrocarbon compositions are needed to help meet the growing demand for middle distillate products, such as jet fuel and diesel fuel. Diesel fuel generally provides a higher energy efficiency in compression ignition engines than automotive gasoline provides in spark combustion engines and has a higher rate of demand growth than automotive gasoline, especially outside the U.S. Further, improved fuel compositions low in aromatics and low in sulfur content are needed to meet the ever tightening quality specifications for diesel fuel as established by industry requirements and governmental regulations.
Propylene oligomers, such as propylene tetramer and propylene pentamer, have been widely used as raw materials for many years in the manufacture of fuel and lubricating oil additives, plasticizers, and surfactants. These branched chain olefins can potentially be a useful source of middle distillate hydrocarbons that are essentially free of aromatics or sulfur. However, branched chain olefins can readily form peroxides which are very undesirable in middle distillate fuels leading to the formation of insoluble gums and other instability products. Peroxides also adversely affect certain fuel system components, such as fuel system elastomers.
It is desirable to develop middle distillate products employing branched chain olefins with improved oxidative stability.